Little is known about the process of sign language development and socialization of deaf and hearing children from extended families of several generations in rural, non-Western communities. This project attempts to fill in the gap with a longitudinal, empirical investigation of sign language development and socialization of deaf and hearing children in a Chatino village. The village, San Juan Quiahije and its outlying hamlet, Cieneguilla, is home to 10 deaf people, including 4 young children, out of a population of 3,628 inhabitants. The deaf people use Chatino Sign Language (CSL), an emerging sign language that is not related to a conventional sign language that is used by deaf people in urban areas of Mexico. The focal children of the project are 4 deaf children of hearing caregivers (3 families) and 4 hearing children of mixed deaf-hearing caregivers, i.e. one deaf parent and one hearing parent (3 families); the ages of all children range from 2;0 to 6;0. The deaf people have not received any formal schooling and have had no training in oral language skills. The deaf people know each other through an extended social network. Although considerable lexical variation exists across families of deaf signers, many CSL signs overlap due to the sharing of co-speech gestures and signs between deaf and hearing community members. The project will produce a large corpus of video- and audio-recorded data of naturalistic and elicited interactions in CSL between deaf and hearing children and their families in their everyday lives, along with a first-pass description of deaf and hearing children's sign language development and language socialization based on 9 consecutive months of fieldwork. Longitudinal participant observations, elicitation methods with toys, pictures, and books, and semi-structured interviews on a monthly basis will be utilized to document language and communicative practices in the sign language-learning environment of the children. A total of six hours of naturalistic data (3 hours) and elicited data (3 hours) from 6 families will be analyzed for comparing the children and their adult caregivers and other high-frequency interactants with respect to (1) communicative behavior including initiation, attention, and gaze and (2) lexical and grammatical structure of the signers' output, for assessing the organization of the communication, types of interactional routines, the sources of input, and the depth and extent of the role of the interactants in the children's development of CSL. Interviews will be conducted to produce rough transcriptions and informed descriptions of samples of conversational events, to prompt metalinguistic discussion of the children's signs, and to prompt discussion of the families' beliefs, attitudes, and knowledge about child-rearing, language and cognitive development, deafness spoken and signed languages, and education. Examining the cultural organization of language and communicative practices, and the social linguistic and environment factors that shape the children's sign language development can provide a better understanding of the children's contribution to the emergence and development of new sign languages.